Many of stators used for motor include coils each of which is formed of a wound conductor having a circular cross-section. As the demands for an increase in efficiency and a reduction in size and weight of a motor have grown in recent years, a high space factor of a conductor in a slot of a stator has been, required.
For mounting a circular cross-section conductor on teeth of a stator core, JP 11(1999)-032457A discloses a configuration that trapezoidal coils and parallel coils are set alternately. However, this configuration requires manufacture of different shaped coils, resulting in an increase in the number of parts, thus leading to cost increase.
From a viewpoint of increasing the space factor of a conductor, on the other hand, some recent stators include coils each of which is formed of a flat rectangular conductor having a square section and is wound by edgewise bending operation. This configuration provides advantages such as an improved space factor and an excellent heat radiation characteristic as compared with a coil-wound stator.
One of techniques using coils of the same shape is disclosed in JP2006-166610A, in which equally-shaped trapezoidal coils are mounted in divided or segmented cores to increase the space factor. This technique allows manufacture of a stator from a single kind of trapezoidal coils.